http.Client in GopherJS has 2 implementations: one based on Fetch API, another based on XMLHttpRequest API. It picks whichever is available in that order. Both of those tend to be available in browsers.

Node doesn't seem to provide either one by default, that's why you need a polyfill (either for Fetch or for XHR) for http.Client to work under node. The problem seems to be that there wasn't a good one, last time people looked. See previous discussion in #586.

Thanks. Worked it out using assistance from #586

Step 1:
Add dependency to npm:
npm install xhr2

Step 2:
Create a imports.inc.js file in the same level as your Go files.

Step 3:
Add global.XMLHttpRequest = require('xhr2'); to the imports.inc.js file.

@shurcooL
It looks like xhr2 does not respect context cancellation despite the documentation stating that it supports abort()

Do you know how I can make cancelling the specific request work?

What I have learnt:

Dont use net/http to make http requests.
Use xhr go package by honnef which uses XMLHttpRequest behind the scenes.

On node js, you need to still add global.XMLHttpRequest = require('xhr2');

I created a package that makes it easy: https://github.com/rocketlaunchr/gopherjs-xhr